TWENTY years ago, Julia Child's "The French Chef" became the first national television program to be closed-captioned for deaf and hearing-impaired viewers. By 1990, when Congress enacted the Television Decoder Circuitry Act, only half a million Americans had purchased special set-top converters to decode the closed captions for viewing, representing less than 1 percent of all television households. But 10 years from now virtually every home will have a television set capable of decoding captions. It is timely to sketch out what this new world will look like, and what needs to be done to ensure its vitality. The new law requires all television sets with picture screens 13 inches or larger sold in the United States to be equipped by July 1, 1993, with built-in decoder circuitry designed to display closed-captioned television transmissions. With new set sales running about 20 million annually, it's a simple matter to project when they will be in virtually everyone's homes. The additional cost for this built-in decoder is estimated to add just $20 to the cost of a new television set. The law will help break a "chicken-and-egg" problem that has plagued the growth of closed-captioned services since their inception. Only since 1989 has all prime-time programming on ABC, CBS, and NBC been captioned. Captioning is much less prevalent on local, daytime, and basic cable programming. The limited penetration of decoders has proven to be a continuing threat to the availability of closed-captioned services. The federal government has supplied roughly one-third of all funding for captioning, with the balance supported by networks, program producers, advertisers, and foundation support, all in the spirit of "doing the right thing." But we must move to a system where captioning can be cost-justified, even profit-motivated. On the demand side, captioning availability will enable other specialized viewers to realize its benefits. The numbers are staggering: Individuals seeking to acquire or improve literacy skills (including 24 million to 27 million functionally illiterate adults), 3 million to 4 million immigrants learning English as a second language, and 18 million children of elementary school age who are learning how to read. Moreover, today's primary users of closed captioning - those who are deaf or hearing-impaired - will benefit because they will not have to incur a $200-$300 investment to purchase a separate decoder nor experience any perceived stigma attached to its purchase or use. This group, comprised of 24 million Americans, includes nearly 40 percent of the elderly population with moderate or severe hearing loss, a number sure to grow as America gets grayer. In short, almost all Americans will be able to benefit in some way by being able to flick a button on their television set to activate the built-in decoder. Since the introduction of the new decoder sets will be gradual, today's network, programming, and advertising entrepreneurs can capitalize on this opportunity by expanding their closed-captioned offerings in the near future, as a way to stimulate this latent demand. For example, although 68 percent of major commercial network programming is captioned today, only 20 percent of local news programming is captioned, and 16 percent of syndicated television programming is captioned. HBO and other pay cable services now caption 36 percent of their fare, but basic cable programming - Turner Network Television, ESPN, and the like - woefully lag behind at 1.2 percent. If captioning availability grows more quickly than the new sets are distributed, we may be able to experience the virtues of supply-side economics in our own living rooms: provide now, profit later. Imagine what it would be like to be able to receive a wide range of captioned programming as soon as a new television set is plugged in. And imagine the competitive advantage that could be achieved by being first to offer expanded captioned programming. Public service seasoned with dollars seems to represent a recipe that should meet approval from The French Chef herself, and serve the rest of us by blending worthy social goals with appropriate marketplace incentives.